A chemical sensor is a device that produces an analytically useful signal as a result of exposure to an analyte/sample matrix. Fluorescent probes that absorb and emit red NIR radiation have special advantages over their UV or visible counterparts, in particular because red or near infrared (NIR) probes have better performance in biological media, e.g. cells or tissues. The longer wavelength excitation and emission of a red or NIR probe is easily distinguished from biological auto-fluorescence than other types of fluorescent probes. As a result, red or NIR probes perform well at deeper penetration (typically several centimeters) compared to other probes in the biological medium.
Existing fluorophores probes such as rhodamine and fluorescein systems are limited in performance due to the shorter emission wavelengths of these probes. In addition, while fluorescein is FDA approved for limited applications, it is unstable to light, and rhodamine, on the other hand, is banned for its known mutagenic properties, which imposes further limitations on the potential applications of these probes.
A need exists for a fluorophore probe that overcomes the limitations of existing fluorophore systems. Such a fluorophore would have a red or NIR emission wavelength and would further be non-toxic and biocompatible with biological media such as cell or tissue cultures. Applications that would benefit from such a red/NIR non-toxic fluorophore probe include fluorescence microscopy, in vivo imaging, flow cytometry, fluorescence correlation spectroscopy, enzyme-linked immunosorbent assays (ELISA), and dye tracing.